Answer: Composites in which strong, stiff fibres are embedded in a softer matrix. GFRP (glass fibres in polyester/epoxy) is cheap and strong; CFRP (carbon fibres in epoxy) is very stiff, strong and light but costly.
Fibre-reinforced composites (FRC): the dispersed phase is in the form of fibres (length much greater than diameter). The load applied to the matrix is transferred to the fibres, which carry most of it, giving high specific strength (strength/density) and specific modulus. Fibres may be continuous and aligned, discontinuous and aligned, or random.
1. Glass-fibre reinforced polymer (GFRP)
- Continuous or chopped E-glass fibres (diameter about 3–20 μm) in a polyester, vinyl ester or epoxy matrix.
- Properties: high strength, good corrosion and chemical resistance, electrical insulator, easy to fabricate, low cost.
- Applications: car bodies and bumpers, boat hulls, pipes and storage tanks, sports goods, water tanks, PCB laminates.
- Limitations: relatively low stiffness (not suitable where rigidity is critical); service temperature limited (most below about 200 °C).
2. Carbon-fibre reinforced polymer (CFRP)
- Carbon (graphite) fibres in an epoxy matrix.
- Properties: very high specific modulus and strength, low density, retains strength at high temperatures, good fatigue and corrosion resistance, low thermal expansion.
- Applications: aircraft and spacecraft structures, racing cars, bicycle frames, tennis rackets, golf shafts, wind-turbine blades, pressure vessels.
- Limitations: high cost, brittle (low impact resistance), difficult to repair and recycle, electrically conducting (galvanic corrosion with metals).
